Most individuals today only receive demonstrations from a very modern design for a Tube Amp'.
The Companies were becoming more 'Corporate Like' the Bean Counters were taken advice from Techies who had not respect for tradition.
Resulting in designs that were enforced to change Topology and Schematics were designed to omit Transformers from the Circuits. Streamlining the component count and casing dimensions took precedent, over overall performance.
If a Amp' with circuits from the period of Halcyon, is discovered and breathed on with a sympathetic approach, using the accuracy of modern components to interface with the Olden World irreplaceable components, now one is 'cooking on gas'.
Barn finds are still big business, as the few in the know, charge substantial amounts to allow another to share in the secret.